The Digital Pulse Waveform Second derivative

A sophisticated approach to contour analysis of the DVP has been developed by investigators in Japan. Takazawa et al.,
Takada et al.  and Imanaga et al. have proposed using the second derivative of the DVP (d2DVP/dt2, sometimes referred to as the ‘acceleration photoplethysmograph’). This facilitates the distinction of five sequential waves called a, b, c, d and e waves .
The relative heights of these waves (b/a, c/a, d/a and e/a ratios), particularly the d/a ratio, have been related to age,
arterial blood pressure , large artery stiffness  and effects of vasoactive drugs .

The b/a ratio has been related to ageing and carotid distensibility .
Following analysis of the correlation of the b/a, c/a, d/a and e/a ratios with age, a more complex ‘ageing index’ was defined as (b–c–d–e)/a .

In a study to assess arterial distensibility in adolescents, the d/a ratio identified individuals at increased risk of developing atherosclerosis. The second-derivative approach has recently been applied to the study of the peripheral pressure pulse. Other mathematical approaches to analysis of the DVP include artificial neural networks, the extraction of periodic components using frequency analysis or nonlinear dynamical analysis.
The physiological and clinical characteristics relating to the derived mathematical parameters, however, have not been clearly identified.